Water Disposal Well Basics

What is water disposal?

Water disposal is a method of dealing with water brought to surface while producing oil and gas wells. This water often contains many contaminants that cannot be disposed of in a safe manner at surface. Water disposal wells and caverns offer a safe and effective way to dispose of this unusable water. 

Who requires water disposal?

Any operator producing hydrocarbons where water is present needs some way to deal with that produced water. There are numerous forms to recycle and re-use water to aid other operations (water-flooding, hydraulic fracturing) but a large amount of this water is un-usable and needs to be disposed of. Water disposal for operators running large frac spreads is in high demand. The large amounts of water needed for fracturing operations produces large amounts of waste products in the form of frac flow-back and produced water. Some of this water can be re-used but a large portion of it is earmarked for disposal. 

How does a water disposal well differ from an oil well?

The main difference between an oil & gas well and a disposal well is that a water disposal well is set up to move fluids in reverse: from the surface into the formation. Tubing is run from surface and a packing device set as close to the perforations as practical. This ensures the fluid being injected is confined to the disposal zone. It also prevents the corrosion of casing in the wellbore since disposal fluid is typically high in salinity and corrosive to steel. 

What is required to develop a water disposal well? 

There are a few things to consider when developing a disposal well. From a business standpoint location and road access is key. From an engineering standpoint the main things to consider are isolation and injection rates. Fluid being disposed of needs to be isolated to the disposal zone. An extensive review of the geology in the area is needed to determine this. You also need to prove hydraulic isolation near wellbore which usually consists of a hydraulic temperature log. Injection rates can be determined from open-hole logs, offsets, cores and DST tests.